Metaphysics is that portion of philosophy which treats of the most general and fundamental principles underlying all reality and all knowledge.

The name

The word metaphysics is formed from the Greek meta ta phusika, a title which, about the year A.D. 70, was related by Andronicus of Rhodes to that collection of Aristotelean treatises which since then goes by the name of the "Metaphysics". Aristotle himself had referred to that portion of philosophy as "the theological science" (theologikê), because it culminated in the consideration of the nature of God, and as "first philosophy" (prôtê philosophia), both because it considered the first causes of things, and because, in his estimation, it is first in importance. The editor, however, overlooked both these titles, and, because he believed that that part of the Aristoteleancorpus came naturally after the physical treatises, he entitled it "after the physics". This is the historical origin of the term. However, once the name was given, the commentators sought to find intrinsic reasons for its appropriateness. For instance, it was understood to mean "the science of the world beyond nature", that is, the science of the immaterial. Again, it was understood to refer to the chronological or pedagogical order among our philosophical studies, so that the "metaphysical sciences would mean, those which we study after having mastered the sciences which deal with the physical world" (St. Thomas, "In Lib, Boeth. de Trin.", V, 1). In the widespread, though erroneous, use of the term in current popular literature, there is a remnant of the notion that metaphysical means ultraphysical: thus, "metaphysical healing" means healing by means of remedies which are not physical.

Definition

The term metaphysics, as used by one school of philosophers, is narrowed down to mean the science of mental phenomena and of the laws of mind, In this sense, it is employed, for instance, by Hamilton ("Lectures on Metaph.", Lect. VII) as synonymous with psychology. Hamilton holds that empirical psychology, or the phenomenology of mind, treats of the facts of consciousness, rational psychology, or the nomology of mind, treats of the laws of mental phenomena, and metaphysics, or inferential psychology, treats of the results derived from the study of the facts and laws of mind. This use of the term metaphysics is unfortunate because it rests on Descartes'sfalse assumption that the method in metaphysics is subjective, in other words, that all the conclusions of metaphysics are based on the study of subjective, or mental, phenemona.

Taking a wider view of the scope and method of metaphysics, the followers of Aristotle and many who do not acknowledge Aristotle as a leader in philosophy define the science in terms of all reality, both objective and subjective. Here five forms of definition are offered which ultimately mean one and the same thing:

Metaphysics is the science of being as being

This is Aristotle's definition (peri tou ontos ê on)  Met., VI, 1026 a, 31). In this definition metaphysics is placed in the genus "science". As a science, it has, in common with other sciences, this characteristic that it seeks a knowledge of things in their causes. What is peculiar to metaphysics is the difference "of being as being". In this phrase are combined at once the material object and the formal object of metaphysics. The material object is being, the whole world of reality, whether subjective or objective, possible or actual, abstract or concrete, immaterial or material, infinite or finite. Everything that exists comes within the scope of metaphysical inquiry. Other sciences are restricted to one or several departments of being: physics has its limited field of inquiry, mathematics is concerned only with those things which have quantity. Metaphysics knows no such restrictions. Its domain is all reality. For instance, the human soul and God, because they have neither colour nor weight, thermic nor electric properties, do not fall within the scope of the physicist's investigation; because they are devoid of quantity, they do not come within the field of inquiry of the mathematician. But, since they are beings, they do come within the domain of metaphysical investigation. The material object of metaphysics is, therefore, all being. As Aristotle says (Met., IV, 1004 a, 34): "It is the function of the philosopher to be able to investigate all things." Its formal object is also "being", or "beingness." The formal object of any science is that particular phase, quality, or aspect of things which interests that science in a specific way. Man, for instance, is the material object of psychology, ethics, sociology, anthropology, philology, and various other sciences. The formal object, however, of each of these is different. The formal object of psychology is mental phenomena and the subject of them; the formal object of ethics is man's relation to his ultimate destiny; that of sociology is man's relation to his fellow-men in institutions, laws customs, etc.; that of anthropology is the origin of man, distinction of races, etc.; that of philology is man's use of articulate speech. The formal object of the physical group generally is the so-called physical properties of bodies, such as light, sound, heat, molecular constitution, in general, etc. The formal object of the mathematical group is quantity; what interests the mathematician is not the colour, heat, etc., of an object, but its size or bulk. Similarly the metaphysician is interested in a specific way neither in the physical nor the mathematical qualities of things, but in their entity or beingness. If, then, physics is the science of being as affected by physical properties, and mathematics is the science of being as possessing quantity, metaphysics is the science of being as being. Since the material object of metaphysics is all being, the metaphysician is interested in everything that is or can be. Since the formal object of his study is, again, being, the point of view of metaphysics is different from that of the other sciences. The metaphysician studies all reality; still, the resulting science is not a summing up of the departmental sciences which deal with portions of reality, because his point of view is different from that of the student of the departmental sciences.

Metaphysics is the science of immaterial being

The first science", says Aristotle (Met., VI, 1026 a, 16), "deals with things which are both separate (from matter) and unmovable". In this connection the scholastics (cf. St. Thomas, ibid.), distinguished two kinds of immaterial:

immaterial quoad esse or immaterial beings, such as God and the human soul, which exist without matter;

immaterial quoad conceptum, or concepts, such as substance, cause, quality, into the comprehension of which matter does not enter.

Metaphysics, in so far as it treats of immaterial beings, is called special metaphysics and is divided into rational psychology, which treats of the human soul, rational theology, which treats of the existence and attributes of God, and cosmology, which treats of the ultimate principles of the universe. Metaphysics in so far as it treats of immaterial concepts, of those general notions in which matter is not included, is called general metaphysics, or ontology, that is, the science of Being. Taking the term now in its widest sense, so as to include both general and special metaphysics, when we say that metaphysics is the science of the immaterial, we mean that whatever exists whether it is an immaterial being or a material being so long as it offers to our consideration immaterial concepts, such as substance or cause, is the object of metaphysical investigation. In this way, it becomes evident that this definition coincides with that given in the preceding paragraph.

Metaphysics is the science of the most abstract conceptions

All science, according to the scholastics deals with the abstract. The knowledge of the concrete individual objects of our experience, with their ever changing qualities and the particular individuating characteristics which make them to be individual (for instance, the knowledge of this tree, of that flower, of this particular animal or person) may be very useful knowledge, but it is not scientific. Scientific knowledge begins, when we abstract from what makes the thing to be individual, when we know it in the general principles that constitute it. The first degree of abstraction is found in the physical sciences which abstract merely from the particularizing, individuating characteristics, and consider the general laws or principles, of motion, light, heat, substantial change, etc. The mathematical sciences ascend higher in the scale of abstraction. They leave out of consideration not only the individuating qualities but also the physical qualities of things, and consider only quantity and its laws. The metaphysical sciences reach the highest point of abstraction. They prescind, or abstract, not only from those qualities physics and mathematics abstract from, but also leave out of consideration the determination of quantity. They consider only Being and its highest determinations, such as substance, cause, quality, action etc. "There is a science", says Aristotle (Met. IV 1003 a, 21) "which investigates being as being, and the attributes which belong to this in virtue of its own nature" (ta toutô huparchonta kath hauto). The objection therefore, that metaphysics is an abstract science would, in the estimation of the scholastics, militate not only against metaphysics but against all the other sciences as well. The peculiarity of metaphysics is not that it is abstract, but that it carries the process of abstraction farther than do the other sciences. This, however, does not make it to be unreal. On the contrary, what is left out of consideration in metaphysics namely individuating qualities, physical movement and specific quantity, derive whatever reality they have as conceptions from the concept, Being, which is the object of metaphysics. Metaphysics, in fact, is the most real of all the sciences precisely because by abstracting from everything else, it has centred, so to speak, its thought on Being, which is the source and root of reality everywhere else in the other sciences.

Metaphysics is the science of the most universal conceptions

This would follow from the consideration offered in the preceding paragraph because, by a well known law of logic, the less the comprehension the greater the extension of a term or concept. The science which deals with the most abstract conceptions must, therefore, be the science of the most universal conceptions. Among our ideas the most universal are Being, and the determinations of it which are called transcendental, namely unity, truth, goodness, and beauty, each of which is coextensive with being itself, according to the formulas, "Every being is one", "Every being is true", etc. Next in universality come the highest determinations of Being in the supreme genera, substance and accident, or, if Being be analyzed in the order of metaphysical constitution, essence and existence, potency and actuality. Very high up in the scale of extension will be cause and effect. All these are included within the range of metaphysical inquiry, and are dealt with in every scholastic manual of metaphysics. "Being in its highest determinations" is, then, another way of describing the object of metaphysics. Where, however, shall we draw the line? What determinations are not highest? For instance, are space and time determinations of Being, which are general enough to be considered in metaphysics? The answer to these questions is to be decided according to the dictates of practical convenience. Many of the problems sometimes included in general metaphysics may conveniently be treated in special parts, such as cosmology and psychology.

Metaphysics is the science of the first principles

This definition also is given by Aristotle (Met. IV, 1003 a, 26). Every science is an inquiry into the causes and principles of things; this science inquires into the first principles and highest causes, not only in the order of existence, but also in the order of thought. It belongs, then, to metaphysics

to inquire into the nature of cause and principle in general and to determine the meaning of the different kinds of causality, formal, material, efficient, and final:

to investigate the first principles in the order of knowledge, and establish the validity, for instance, of the principles of identity and contradiction.

All these definitions are expressions of the Aristoteleandoctrine that metaphysics, like physics and mathematics, is a science of reality, it being beyond the scope of metaphysics to inquire whether reality is, or is not, given in experience. This question, which is a fundamentally important one in modern philosophy was discussed by the scholastics in that portion of logic which they called critical, major logic, or applied logic, but which is now generally called epistemology (see LOGIC). Nowadays however, the epistemological problem, by a fatal mistake of method, is assigned to metaphysics, and the result is a confusion between the two branches of philosophy, viz. metaphysics and epistemology. In works like Fullerton's "System of Metaphysics" (New York, 1906) and Hodgson's "Metaphysics of Experience" (London, 1898) no attempt is made to separate the two.

The rejection of metaphysics

The Rejection of Metaphysics, by many schools of philosophy in modern times, is one of the most remarkable developments of post-Cartesian philosophy. A difference in the point of view leads to a very great divergence in the estimate based on metaphysical studies. On the one side we have the verdict that metaphysics is nothing but "transcendental moonshine", on the other, the opinion that it is "organized common sense", or "an unusually obstinate effort to think accurately". Materialism, naturally, objects to the claim of metaphysics to be a science of the immaterial. If nothing exists except matter, a science of the immaterial has no justification. Materialists, however, forget that the assertion, "Nothing exists except matter", is either a summing up of the individual experience of the materialist himself, meaning that he as never experienced anything except matter and manifestations of matter, and then the assertion is merely of biographical interest; or it is an affirmation regarding possible human experience, a declaration of the impossibility of immaterial existence, and in that sense it is a statement which in itself has a metaphysical import. Materialism is, in fact, a metaphysical theory of reality and is a contribution to the science which it professes to reject. Philosophical agnosticism, which is derived ultimately from Kant'sdoctrine of the unknowableness of noumenal reality (Ding an sich), rejects metaphysics on the ground that while the immaterial does, indeed, exist, it is unknown and must remain unknowable to the speculative reason. Kant maintained that all metaphysical reasoning, since it attempts by means of the speculative reason to go beyond experience, is doomed to failure, because the a priori forms which the understanding imposes on the empirical data of knowledge modify the quality of that knowledge by making it to be transcendental, but do not extend it beyond the realm of actual sense experience. The followers of Kant stigmatize as intellectual formalism the view that the speculative reason does actually attain ultra-empirical knowledge. This is the contention of the modernists and other Catholic writers who are more or less influenced by Kant. These decry rational metaphysics and offer as a substitute a metaphysics based on sentiment, vital activity, or some other non-rational foundation.

The answer to this line of thought is a denial of its fundamental tenet, the doctrine, namely, that the rational faculty cannot attain a knowledge of the essential or noumenal natures of things. Gratuitous assertion is often best refuted by categorical denial. The rejection of metaphysics by the materialist and the Kantianagnostic does not meet the full approval of the idealist. Instead of banishing metaphysics from the republic of the sciences, the idealist, having deprived it of its scientific character, elevates it to the rank of æsthetic preeminence side by side with poetry. He considers that it furnishes a point of view from which to contemplate the beauty, harmony, and value of those things which science merely explains. He holds that it is not the province of metaphysics to assign reasons or causes, but to furnish motives for action and enhance the value of reality. For him, its uplifting and regenerating function is entirely independent of its alleged ability to explain: he considers metaphysics to be, not an ontology, or science of reality, but a teleology, or application of the principle of purpose. That this is a function of metaphysics no one will deny. It is only one function, however, and unless the doctrine of final causes has its foundation in a doctrine of formal and efficient causes, teleological metaphysics is a castle in the air. Finally, the positivist, and the scientist whom the positivist has influenced, reject metaphysics because all our knowledge is confined to facts and the relations among facts. To attempt to go beyond facts and the succession or concomitance of facts is to essay the impossible. Causes, essences, and so forth, are terms which clothe in fictitious garb our ignorance of the real scientific explanation. The whole gist of positivism is contained in Hume's verdict that "it is impossible to go beyond experience". This psychological dictum is accepted by the philosophical positivist, as the death sentence of metaphysics. With the scientist, however, other considerations weigh more than the psychological argument. The scientist points to the present condition of metaphysics; he calls attention to the fact that, while the physical sciences have advanced by leaps and bounds, metaphysics is still grappling with the most fundamental problems and has not even settled the questions on which its very existence depends. The condition of metaphysics is, indeed, such as to invite the contempt and provoke the disdain of the scientist; the fault, however, may lie not so much in the claims of metaphysics as in the vagaries of the metaphysicians.

Relation of metaphysics to other sciences

The consideration of the relation in which metaphysics stands, or ought to stand, to the other sciences should result in a refutation of the positivist contention that metaphysics is useless. In the first place, metaphysics is the natural co-ordinating science which crowns the unifying efforts of the other sciences. It accomplishes in the highest plane of knowledge that process of unification towards which the humanmind tends irresistibly. Without it, the explanations and co-ordinations attained in the lower sciences would be, perhaps, satisfactory within the limits of those sciences, but would fail to meet the requirements of that unifying instinct which the mind tends to apply to knowledge in general. So long as the mind of the knower is one, it is impossible not to attempt to bring under the most general conceptions and principles the conclusions of the various sciences. That is the task of metaphysics. Whenever we look around among the contents of the mind and try to discover order and hierarchical arrangement among them, we are attempting a system of metaphysics. In the next place, the process of explanation which belongs to each of the lower sciences, if pursued far enough, brings us face to face with the demand for a metaphysical explanation. Thus, the chemical problem of atomic or proto-atomic constitution of bodies leads inevitably to the question, "What is matter?" The biological problem of the nature and origin of life brings us to the point where it is imperative to answer the query, "What is life?" The questions: "What is substance? What is a cause? What is quantity?" are additional examples of problems to which physics, mathematics, etc., finally lead. Indeed, the world of science is completely surrounded by the metaphysical world, and every path of investigation brings us to a highroad of inquiry which sooner or later crosses the border and leads us into metaphysics. When therefore, the scientist rejects metaphysics, he suppresses a natural and ineradicable tendency of the individual mind towards unification and, at the same time, he tries to put up in every highway and byway of his own science a barrier against further progress in the direction of rational explanation. Besides, the cultivation of the metaphysical habit of mind is productive of excellent results in the sphere of general culture. The faculty of appreciating principles as well as facts is a quality which cannot be absent from the mind without detriment to that symmetry of development wherein true culture consists. The scientist who objects to metaphysics, rightly condemns the metaphysician who disdains to consider facts. He himself, unless he cultivate the metaphysical powers of his mind, is in danger of reaching the point where he is incapable of appreciating principles. Both the empirical talent for ascertaining facts and the metaphysical grasp of principles and laws are necessary for the rounding out of man's mental powers, and there is no reason why they should not both be cultivated.

Relation of metaphysics to theology

The nature of metaphysics determines its essential and intimate relation to theology. Theology, it need hardly be said, derives its conclusions from premises which are revealed, and in so far as it does this it rises above all schools of philosophy or metaphysics. At the same time, it is a human science, and, as such, it must formulate its premises in exact terminology and must employ processes of human reasoning in attaining its conclusions. For this, it depends on metaphysics. Sometimes, indeed, as when it deals with the supernatural mysteries of faith, theology acknowledges that metaphysical conceptions are inadequate and metaphysical formulae incompetent to express the truths discussed. Nevertheless, if theology had no metaphysical formularies to rely upon, it could neither express its premises nor deduce its conclusion in a scientific manner. Again, theology relies on metaphysics to prove certain truths, called the preambula, which are not revealed but are nevertheless presupposed before revelation can be considered reasonable or possible. These truths are not the foundation on which we rest our supernaturalfaith. If they should fail, faith would not suffer, though theology should then be rebuilt on another foundation. Furthermore, metaphysics, as Aristotle pointed out, culminates in the discussion of the existence and nature of God. God is the object of theology. It is only natural, therefore, that metaphysics and theology should have many points of contact, and that the latter should rely on the former. Finally, since all truth is one, both in the source from which it is derived, and in the subject, the humanmind, which it adorns, there must be a kinship between two sciences which, like theology and metaphysics, treat of the most important conceptions of the humanmind. The difference in the manner of treatment, theology relying on revelation, and metaphysics on reason alone, does not affect the unity of purpose and the final harmony of the conclusions of the two sciences.

But, while theology thus derives assistance from metaphysics, there can be no doubt that metaphysics has derived advantages from its close association with theology. Pre-Christian philosophy failed to arrive at precise metaphysical determinations of the notions of substance and person. This defect was corrected in part by Origen, Clement, and Athanasius, and in part by their successors, the scholastics, the impulse in both cases being given to philosophical definition by the requirements of theological speculation concerning the Blessed Trinity. Pre-Christian philosophy failed to give a coherent, satisfactory account of the origin of the world: Plato's myths and Aristotle'sdoctrine of the eternity of matter could not long continue to satisfy the Christian mind. It was, once more, the Alexandrian School of Christian metaphysics that, by elaborating the Biblical conception of creation ex nihilo, gave an explanation of the origin of the universe which is satisfactory to the metaphysician as well as to the theologian. Finally, the Catholic doctrine of Transubstantiation, as discussed by the scholastics, gave occasion for a more definite and detailed determination of the metaphysical conception of accident in general and of quantity in particular.

The method of metaphysics

Among the objections most frequently urged against metaphysics, especially against scholastic metaphysics, is the unscientific character of its method. The metaphysician, we are told, pursues the a priori path of knowledge; he neglects or even condemns the use of the a posteriori empirical method which is employed with so much profit in the investigation of nature; he spins as Bacon says, the threads of his metaphysical fabric from the contents of his own mind, as the spider spins her web from the substance of her body, instead of gathering from every source in the world around him the materials for his study, and then working them up into metaphysical principles, as the bee gathers nectar from the flowers and elaborates it into honey. In order to clear up the misunderstanding which underlies this objection, it is necessary to remark that there are three kinds of method:

the a priori, which, assuming certain self-evident postulates, maxims, and definitions to be true, proceeds deductively to draw conclusions implicated in those assumptions;

The subjective a posteriori method, which, from an examination of the phenomena of consciousness builds up empirically, that is, inductively, conclusions based on those phenomena;

the objective a posteriori method, which builds on the facts of experience in general in the same way as the subjective method builds on the facts of introspection.

The second method is pre-eminently the method of the Cartesians, who, like their leader, Descartes, strive to build the whole edifice of philosophy on the foundation furnished by reflection on our thought-processes: Cogito, ergo sum. It is also the method of the Kantians, who, rejecting the psychological basis of metaphysics as unsafe, build on the moral basis, the categorical imperative: their line of reasoning is "I ought, therefore I am free", etc. The third is the method of those who, rejecting the Aristotelean conceptions, essence, substance, cause etc., substitute so-called empirical conceptions of force mass, and so forth, under which they attempt to subsume in a system of empirico-critical metaphysics the conceptions peculiar to the various sciences. The first method is admittedly unscientific (in the popular sense of the word) and is adopted only by those philosophers who, like Plato, consider that the true source of philosophicalknowledge is above us not in the world around and beneath us. If the formula universalia ante rem (see UNIVERSALS) is taken in the exclusive sense, then we may not look to experience, but to intuition of a higher order of truth, for our metaphysical principles. It is a calumny which originated in ignorance perhaps, more than in prejudice, that the scholastics followed this a priori method in metaphysics. True, the scholastic philosopher often invokes such principles as "Agere sequitur esse" "Quidquid recipitur per modum recipientis recipitur" etc. and therefrom deduces metaphysical conclusions. If, however, we examine more closely, if we go back from the "Summa", or text-book, where the adage is quoted without proof, to the "Commentary on Aristotle" where the axiom is first introduced, we shall find that it is proved by inductive or empirical argument, and is therefore a legitimate premise from which to deduce other truths. In point of fact, the scholastics use a method which is at once a priori and a posteriori, and the latter both in the objective and the subjective sense. In their exposition of truth they naturally use the a priori, or deductive, method, In their investigation of truth they explore empirically both the world of mental phenomena within us, and the world of physical phenomena without us, for the purpose of building up inductively those metaphysical principles from which they proceed. It may be conceded that many of the later scholastics are too ready to invoke authority instead of investigating; it may be conceded, even, that the greatest of the scholastics were too dependent on books, especially on Aristotle's works, for their knowledge of nature. But, in principle, at least, the best representatives of scholasticism recognized that in philosophy the argument from authority is the weakest argument, and if the circumstances in which they lived and wrote made it imperative on them to master the contents of Aristotle's writings on natural science, it must, nevertheless, be granted by every fair minded critic that in metaphysics at least they improved on the doctrines of the Stagyrite.

History of metaphysics

The history of metaphysics naturally falls into the same divisions as the history of philosophy in general. In a brief outline of the course which metaphysical speculation has followed, it will be possible to consider only the principal stages, namely (1) Hindu philosophy, (2) Greek philosophy, (3) Early Christian philosophy, (4) Medieval philosophy, (5) Modern philosophy.

Hindu philosophy

Of all the peoples of antiquity, the Hindus were the most successful in rising immediately from the mythological explanation of the universe to an explanation in terms of metaphysics. Apparently without passing through the intermediary stage of scientific explanation, they reached at once the heights of the metaphysical point of view. From polytheism or monotheism they proceeded very early to pantheism, and from that to a monistic metaphysical conception of reality. Their starting-point was the realization that man is born into a state of bondage and that his chief business in life is to deliver himself from that condition by means of knowledge. The knowledge, they taught, which avails most in the struggle for freedom is this: the world of sense phenomena is an illusion (mâya), all real things are identical in the one supreme substance, the soul is part of this real substance, and will ultimately return to the Whole. The real substance is, as Max Müller remarks, spoken of as a neuter, and in this doctrine "is contained in nuce a whole system of philosophy" ("Six Systems of Indian Philosophy", London, 1899, p. 60). The first, and most important of all truths, then, is that reality is one, and each of us is identical with the All: "That art thou" is the highest expression of self-knowledge, and the gate to all salutary truth. Thus, the Hindus, actuated by an ethical, or ascetic, motive, attained a metaphysical formula to which they reduced all reality.

Greek philosophy

The first Greek philosophers were students of nature. They were actuated not by an ethical motive, but by a kind of scientific curiosity to know the origins of things. There was no metaphysician among the Ionians (see IONIAN SCHOOL OF PHILOSOPHY). Out of the problem of origins, however, the metaphysical problem was developed by the Eleatics and Heraclitus. These philosophers considered that the explanations of the Ionians  that the world originated from water or air  were too naïve, relied too much on the verdict of the senses. Consequently, they began to contrast the real truth which the mind (nous) sees, and the illusory truth (doxa) which appears to the senses. The Eleatics, on the one hand, asserted that the permanent element, which they called Being, alone exists, and that change, motion, and multiplicity are illusions. Heraclitus, on the other hand, reached the conclusion that what mind reveals is change, which alone is real, while permanency is only apparent, is, in fact, an illusion of the senses. Thus, these thinkers thrust into the foreground the problem of change and permanency. They themselves, were not, however, wholly free from the limitations which confined the earlier Ionians to a physical view of the problems of philosophy. They formulated metaphysical principles of reality, but both in the language which they used and in the mode of thought which they adopted, they seemed to be unable to rise above the consideration of matter and material principles. Nevertheless, they did immense service to metaphysics by bringing out clearly the problem of change.

Socrates was primarily an ethical teacher. Still, in laying the foundation of ethics he formulated a theory of knowledge which had immediate application to the problem of metaphysics. He taught that the contrast and apparently irreconcilable contradiction between the verdict of the mind and the deliverance of the senses disappear if we determine the scientific conditions of trueknowledge. He held that these conditions are summed up in the processes of induction and definition. His conclusion, therefore, is, that out of the data of the senses, which are contingent and particular, we may form concepts, which are the elements of true scientific knowledge. He himself applied the doctrine to ethics.

Plato, the pupil of Socrates, carried the Socratic teaching into the region of metaphysics. If knowledge through concepts is the only trueknowledge, it follows, says Plato, that the concept represents the only reality, and all the reality, in the object of our knowledge. The sum of the reality of a thing, is therefore the Idea. Corresponding to the internal, or psychological, world of our concepts is not only the world of our sense experience (the shadow-world of phenomena), but also the world of Ideas, of which our world of concepts is only a reflection, and the world of sense phenomena, a shadow merely. That which makes anything to be what it is, the essence, as we should call it, is the Idea of that thing existing in the world above us. In the "thing" itself, the phenomenon presented by the senses, there is a participation of the Idea, limited, disfigured and debased by union with a negative principle of limitation called matter. The metaphysical constituents of reality are, therefore, the Ideas as positive factors and this negative principle. From the Ideas comes all that is positive, permanent, intelligible, eternal in the world. From the negative principle come imperfection, negation, change, and liability to dissolution. Thus, profiting by the epistemological doctrines of Socrates, without losing sight of the antagonistic teachings of the Eleatics and of Heraclitus, Plato evolved his theory of Ideas as a metaphysical solution of the problem of change, which had a baffled his predecessors.

Aristotle also was a follower of Socrates. He was influenced, too, by the theory of Ideas advocated by his master, Plato. For, although he rejected that theory, he did so after a study of it which enabled him to view the problem of change in the light of metaphysical principles. Like Plato, he accepted the Socraticdoctrine that the only trueknowledge is knowledge of concepts. Like Plato, too, he inferred from this that the concept must represent the reality of a thing. But unlike Plato, he made at this point an important distinction. The reality, he taught, which the concept represents is in the thing which it constitutes, not as an Idea, but as an essence. He considers that the Platonic world of Ideas is a meaningless duplication of things: the world of essences is in, not above, nor beyond, the world of phenomena: there is, consequently, no contradiction between sense experience and intellectualknowledge: the metaphysical principles of things are known by abstraction from those individuating qualities, which are presented in sense knowledge; the knowledge of them is ultimately empirical, and not to be explained by an intuition which we are alleged to have enjoyed in a previous existence. In the essence of material things Aristotle further distinguished a twofold principle, namely the Form, which is the source of perfection, determinateness, activity and of all positive qualities, and the Matter, which is the source of imperfection, indetermination, passivity and of all the limitations and privations of a thing. Coming now to the borderland of metaphysics and physics, Aristotle defined the nature of causality, and distinguished four supreme kinds of cause, Material, Formal, Efficient and Final (see CAUSE). In addition to these contributions to the solution of the problem of change, which had, by historical evolution, become the central problem of metaphysics, Aristotle contributed to metaphysics a discussion of the nature of Being in general, and drew up a scheme of classification of things which is known as his system of Categories. He is least satisfactory in his treatment of the problem of the existence and nature of God, a question in which, as he himself admits, all metaphysical speculation culminates.

After the time of Aristotle, philosophy among the Greeks became centered in problems of human destiny and human conduct. The Stoics and the Epicureans, who were the chief representatives of this tendency, devoted attention to questions of metaphysics, only in so far as they considered that such questions may influence human happiness. As a result of this subordination of metaphysics to ethics, the pantheistic materialism of the Stoics and the materialistic monism of the Epicureans fall far short of the perfection which the doctrines of Plato and Aristotle attained. Contemporaneously with the Stoic and Epicurean schools, a new school of Platonism, generally called Neo-Platonism, interested itself very much in problems of asceticism and mysticism, and, in connection with these problems, gave a new turn to the drift of metaphysical speculation. The Neo-Platonists, influenced by the monotheism of the Orientals, and, later by that of the Christians, took up the task of explaining how the manifold, diversified, imperfect world originated from the One, Unchangeable, and Perfect Being. They exaggerated the Platonicdoctrine of matter to the point of maintaining that all evil, moral as well as physical, originates from a material source. At the same time, they ascribed to the spiritualized Ideas which they called daimones (spirits) all actuality, intelligence, and force in the whole universe. These intelligences were derived, they said, from the One by a process of emanation, which is akin to the "streaming forth" of light from the illuminating body. This system of metaphysics teaches, therefore, that the One, and intelligences derived from the One, are the only positive principles, while matter is the only negative principle of things. This is the system which was most widely accepted in pagan circles during the first centuries of the Christian era.

Early Christian philosophy

The first heretics among the Christian thinkers were influenced in their philosophy by Neo-Platonism. For the most part, they adopted the Gnostic view (see GNOSTICISM) that in the last appeal, the test of Christiantruth is not the official teaching of the Church or the exoteric doctrine of the gospels, but a secret gnosis, a body of doctrine imparted by Christ to the chosen few. This body of doctrine was in reality a modified Neo-Platonism. Its most salient point was the theory that evil is not a creation of God but the work of the devil. The problem of evil thus came to occupy an important place in the philosophical systems of orthodoxChristian thinkers down to the time of St. Augustine. Other problems, too, claimed special attention, notably the question of the origin of the universe. From the theological controversies concerning the mysteries of the Trinity and the Incarnation, arose the discussion of the meaning of nature, substance, and person. From all these sources sprang the ChristianNeo-Platonism of the great Alexandrian School, which included Clement and Origen, and the later phase of ChristianPlatonism exemplified by St. Augustine. In the philosophy of St. Augustine we have the greatest constructive effort of the Christian mind during the Patristic Era. It is a philosophy which centres in the problems arising from the nature of God, and the nature and destiny of the human soul: The most crucial of these problems is that of the existence of evil. How can evil exist in a world created and governed by a God, Who is at once supremely good and all-powerful? Rejecting the Manichean theory that evil has an origin distinct from God, St. Augustine devotes all his efforts to showing, from the nature of evil, that it does not demand a direct efficient act on the part of God, but only a permissive act and that this toleration of evil is justified by the gradation of beings which results from the existence of imperfection, and which is essential to the harmony and variety of the universe in general. Another question which attains a good deal of prominence in St. Augustine's metaphysics is that of the origin of the world. All things, he teaches, were created at the beginning, material creatures as well as angels, and the subsequent appearance of plants, animals, and men in a chronological series is merely the development in time of those "seeds of things" which were implanted in the material world at the beginning. However, St. Augustine is careful to make an exception in the case of the individual human soul. He avoids the doctrine of preexistence which Origen had taught, and maintains that the individual soul originates at the same time as the body, although he is not prepared to decide definitively whether it originates by a distinct creative act or is derived from the souls of the child's parents (see TRADUCIANISM).

Medieval philosophy

The first scholastic philosophers devoted their attention to the discussion of logical problems arising out of the interpretation of the texts which were studied in the schools, such as Porphyry's "Isagoge", and Boethius's translation of portions of Aristotle's "Organon". From these discussions they passed to problems of psychology, but it was not until the end of the twelfth century, when Aristotle's metaphysical treatise and his works on psychology became accessible in Latin, that scholastic metaphysics rose to the dignity and proportions of a system. By way of exception, John the Scot (see ERIUGENA), as early as the first half of the ninth century, developed a highly wrought system of metaphysical speculation characterized by idealism, pantheism, and Neo-Platonicmysticism. In the eleventh century the school of Chartres, under the influence of Platonism, discussed in a metaphysical spirit the problems of the nature of reality and the origin of the universe.

The philosophy of the thirteenth century, represented by Alexander of Hales, St. Bonaventure, Roger Bacon, Albert the Great, St. Thomas, and Duns Scotus, accorded to metaphysics its place as the science which completes and crowns the efforts of the mind to attain a knowledge of things human and divine. It acknowledged the importance of the relation which metaphysics bears, on the one hand, to the other portions of philosophy, and, on the other hand, to the science of theology. Fundamentally Aristotelean in its conception of method and scope, the metaphysics of the golden age of scholasticism departed from Aristotle's teaching only to supply the defects and correct the faults which it detected in Aristotle's philosophy. Thus, it worked out on Aristotelean lines the problems of person and nature, substance and accident, cause and effect; it took up and carried to higher systematic development St. Augustine's reconciliation of evil with the goodness of God; it elaborated in detail the question of the nature of matter and the origin of the universe by God's creative act. At the same time, the metaphysics of the schools was obliged to face new problems which were thrust on the attention of the schoolmen by the exegetical and educational activity of the Arabians. Thus, it drew the line of distinction between Theism and Pantheism, discussed the question of fatalism and free will, and rejected the Arabian interpretation of Aristotle which jeopardized the doctrine of personal immortality. Towards the end of the scholastic period the appearance of the anti-metaphysicai nominalism of Occam, Durandus, and others had the effect of driving some of the later schoolmen to adopt an extreme a priorism in philosophy, which more than any other single cause contributed to bring about the antagonism between metaphysics and natural science, which marks the era of scientific discovery. This condition, though widespread, was not, however, universal. Men like Francisco Suárez and other great commentators continued down to the seventeenth century to present in their metaphysical treatises the best traditions of the scholasticism of the thirteenth century.

Modern philosophy

At the beginning of the modern era we find a divergence of opinion concerning the scope and value of metaphysical speculation. On the one hand, Bacon, while himself retaining the name metaphysics to designate the science of the essential properties of bodies, is opposed to the metaphysical philosophy of the scholastics, and chiefly because that philosophy gave too much prominence to final causes and the study of the mind. On the other hand, Descartes, while declaring that "philosophy is a tree, which has metaphysics for its root", understands that the science of metaphysics is based exclusively on the data of the subjective consciousness. Spinoza accepts this restriction, implicitly at least, although his explicit main philosophy is ethical, namely to present that view of reality which will lead to the deliverance of the soul from bondage. Leibniz takes a more objective view. He tries to adopt a definition of reality which will reconcile the idealism of Plato with the results of scientific research, and he aims at harmonizing the materialism of the atomists with the spiritualism of the scholastics. Locke, by limiting all our knowledge to the two sources, sensation and reflection precludes the possibility of metaphysical speculation beyond the facts of experience and of consciousness. In fact, he maintains (Essay, IV, 8) that all metaphysical formulae, when they are not merely tautological and, therefore "trifling", have only a hypothetical formulae. This line of thought is taken up by Hume who emphatically declares that "it is impossible to go beyond experience", and by Mill, who maintains the hypothetical nature of all so-called necessarytruth, mathematical as well as metaphysical. The same position is taken by the French sensists and materialists of the eighteenth century. Berkeley, although his professed aim was merely "to remove the mist and veil of words" which hindered the clear vision of the truth, passed from empirical immaterialism to a system of Platonicmysticism based on the metaphysical principle of causality.

Beginning with Kant, the question of the existence and scope of metaphysical science assumes a new phase. Metaphysics is now the science which claims to know things in themselves, and as Kant sees it, all post-Cartesian metaphysics is wrong in its starting-point. Kant holds that both the empiricist's rejection of metaphysics and the dogmatist's defence of it are wrong. The empiricist is wrong in asserting that we cannot go beyond experience: the dogmatist is wrong in affirming that we can go beyond experience by means of the theoretical reason. The practical reason, the faculty of moral consciousness, can alone take us beyond experience, and lead us to a knowledge of things in themselves. Practical reason, therefore, or the moral law, of which we are immediately conscious, is the only foundation of metaphysical science. The successors of Kant, namely, Fichte, Schelling, Hegel, Schopenhauer, and Von Hartmann, no matter how much they may differ in other respects, hold that the aim of metaphysics is to attain the ultra-empirical, or absolute, reality, whether this be called self (Fichte), the absolute of indifference (Schelling), the dynamic absolute, spirit or Idea (Hegel), the Will (Schopenhauer), or the Unconscious (Von Hartmann). Another group, the empiro-critics, who also acknowledge their dependence on Kant, assign to metaphysics the task of discussing the fundamental principles of knowledge by means of a critical examination of experience. Finally, there is among German philosophers of our own day an inclination to use the word metaphysics to designate any view of reality which, transcending the limits of the particular sciences, strives to combine and relate the results of those sciences in a synthetic formula (Weltanschauung).

Englishphilosophers either define metaphysics in terms of mental phenomena, as Hamilton does, or restrict its field of inquiry to the problem of the value of knowledge, thus confounding it with epistemology, or go over to the Hegelian point of view that metaphysics is the science of the genesis and development of dynamic categories of reality. The evolutionist school, represented by Herbert Spencer, while they deny the cogency of "metaphysical reasonings", attempt a general synthesis of all truth under the evolutionist formula, which is in reality metaphysics in disguise. Their effort in this direction is, at least, an acknowledgement of the justice of the scholastic claim that there must be a hegemonic science which unifies and co-ordinates in an articulate system the conclusions of the various sciences, and which corrects the tendencies of those sciences towards a specialization which ends in fragmentation.

In so far as pragmatism, represented by James, Dewey, and Schiller, rejects absolute truth, it may be said to cut the ground from under metaphysics. Nevertheless, the latest phase of pragmatism, in which interest is shifted from the epistemological problem to the question, What is reality? is manifestly a step towards a rehabilitation of metaphysics. An analysis of reality is followed inevitably by an attempt to synthesize. The pragmatic synthesis, naturally, will have for its foundation neither the law of entity, as that being is being, nor the law of contradiction, that being is not not-being, but some principle of "value", akin to that of the Werth-Theorie of Lotze. Of quite special interest is the attempt on the part of Professor Royce to interpret reality in terms of loyalty. With the exception, then, of Trendelenburg's "Studies", and critical expositions of the text of Aristotle, the only philosophical literature in recent times which adopts the Aristotelean view of the nature and scope of metaphysics, is that which has come from the pens of the Neo-Scholastics. The Neo-Scholasticdoctrine on at least one point in metaphysics is given in the following paragraph.

Doctrine of being

The three ideas which are most important in any system of metaphysics are Being, Substance, and Cause. These have a decisive influence, and may be said to determine the character of a metaphysical system. Substance and Cause are treated elsewhere under separate titles (see CAUSE and SUBSTANCE). It will, therefore, be sufficient here to give the outlines of the scholastic doctrine of Being, which, indeed, is the most fundamental of the three, and decides, so to speak, beforehand, what the scholastics teach regarding Substance and Cause.

(1) Description of Being

Being cannot he defined (a) because a definition, according to the scholastic formula, must be "by proximate genus and ultimate difference", and Being, having the widest extension, cannot be included in any genus; (b) because a definition is the analysis of the comprehension of a Concept, and Being, having the least comprehension, is, as it were, indivisible in its comprehension, resisting all efforts to resolve it into simpler thought elements. Nevertheless, Being may be described. The word "Being", taken either as a participle or as a noun, has reference to the "act" of existence. Whatever exists, therefore, is a Being, whether it exists in the mind or outside the mind, whether it is actual or only potential, whether it requires a subject in which to inhere or is capable of subsisting without a subject of inherence. Thus, the broadest division of Being is into, notional, which exists only in the mind (ens rationis), and, real, which exists independently of the created world (ens reale). Real Being is further divided into the potential and the actual. This is an important point of scholastic teaching, which is sometimes overlooked in the exposition and still more in the criticism of scholasticism. For the scholastics, the real world extends far beyond the actual world of our experience or even of possible experience. Beyond the realm of actually existing things they see a world of tendencies, potencies, and possibilities which are truly real. The oak is really present, though only potentially, in the acorn; the painting is really, though only potentially, present, in the mind of the artist; and so, in every case, before the effect becomes actual it is really present in the cause in the measure in which its actual existence depends on the cause.

(2) Relation of Being to Other Concepts

Scholasticpsychology, adopting Aristotle'sdoctrine that all our ideas are acquired through the senses, teaches that the first knowledge which we acquire is sense-knowledge. Out of the material furnished by the senses the mind elaborates ideas or concepts. The first of these ideas is the most general, the poorest in representative content, namely, the idea of "Being". In this sense, therefore, the idea of being, or, more correctly, perhaps, the idea of "something", is the first of all our ideas.

Turning, now, to the logical relation, how, ask the scholastics, is the idea of Being predicated of the lower or less general concepts, such as substance, accident, body, plant, tree, etc.? In the first place, the predicate being is never univocally affirmed of lower concepts, because it is not a genus. Neither is it predicated equivocally, because its meaning when predicated of substance, for example, is not entirely distinct from its meaning when predicated of accident. The predication is, therefore, analogical. What, then, is the relation, in comprehension, between Being and the lower concepts? It is obvious that the lower concept has greater comprehension than Being. But can it be said that the lower concept adds to the comprehension of Being? Manifestly, that is impossible, because if anything distinct from being is added to being, what is added is nothing, and there is no addition. The schoolmen, therefore, teach that the lower concept simply brings out in an explicit manner a mode or modes of being which are contained implicitly but not expressed in the higher concept, Being. The comprehension, for example, of substance is greater than that of being. Nevertheless it is not correct to say that, Substance = Being + a; for if a is distinct from the term Being, to which it is added, it must be Nothing. The truth, then, is that Substance brings out explicitly a mode (namely the power of existing without a subject in which to inhere) which is neither explicitly affirmed nor explicitly denied but only implicitly contained in the concept of Being.

(3) Being and Nothing

Being, therefore, has a comprehension, which, though it is the least of all comprehensions, is definite. It is not a bare, empty concept, and, therefore, equal to "nothing", as the Hegelians teach. This doctrine of the scholastics is the line of demarcation between Aristoteleanism on the one hand and Hegelianism on the other. Aristotle teaches that being has a definite comprehension, that, therefore, the fundamental law of thought as well as the basic principle of reality is the identity of Being with itself: Being = Being, A is A, or Everything is what it is. Hegel does not deny that this Aristotelean principle is true. He holds, however, that Being has an indeterminate comprehension, a comprehension which is dynamic or, as it were, fluent. Therefore, he says, the principle Being = Being, A is A, or Everything is what it is, is only part of the truth, for Being is also equal to Nothing, A not-A, Everything is its opposite. The full truth is: Being is Becoming; no static or fixed formula is true; everything is constantly passing into its opposite. The consequences which follow from this fundamental divergence of doctrine regarding Being are enormous. Not the least serious of these is the Hegelian conclusion that all reality is dynamic and that God Himself is a process.

(4) Being, Existence, and Essence

As wisdom (sapientia) is that by which a person is wise (sapere), so essence (essentia) is that by which a thing is (esse). If one inquires what is the intrinsic cause of a person being wise, the answer is, wisdom; if one asks what is the intrinsic cause of existence, the answer is, essence. Essence, therefore, is that by which a thing is what it is. It is the source of all the necessary and universal properties of a thing, and is itself necessary, universal, eternal, and unchangeable. The act to which it refers is existence, in the same way as the act to which wisdom refers, is the exercise of wisdom (sapere). Both existence and essence are realities, the one in the entitative order, the other in the quiddative order. Of course, the existence of a notional being (ens rationis) is only notional; its essence, too, is notional. But in the case of a real, created Being, the existence is one kind of reality, a real actuality, and the essence is another kind of reality, a reality in the potential order. This doctrine of the real distinction between essence and existence in real created beings is not admitted by all scholastic philosophers. Francisco Suárez, for instance, and his school, hold that the distinction is only logical or notional; the Scotists, too, maintain that the distinction in question is less than real. The Thomists, on the contrary, hold that in God alone essence and existence are identical, that in all creatures there is a real distinction, because in creatures existence is participated, diversified, and multiplied, not by reason of itself but by reason of the essence which it actualizes. There is much controversy not only over the question itself, but also concerning the interpretation of the words of St. Thomas, although there seems very little ground for denying that in the work "De Ente et Essentia" the Angelic Doctor holds a real distinction between essence and existence.

(5) Transcendental Properties of Being

Equally extensive with the concept of Being are the concepts good, true, one, and beautiful. Every being is good, true, one, and beautiful, in the metaphysical sense, or as the scholastics expressed it, Being and Good are convertible, Being and True are convertible, etc. (Bonum et ens convertuntur, etc.). Goodness, in this sense, means the fullness of entity or perfection which belongs to each being in its own order of existence; truth means the correspondence of a thing to the idea of it, which exists in the Divine Mind; oneness means the lack of actual division, and beauty means that completeness, harmony or symmetry of essential nature which is only an aspect of truth and goodness. These properties, goodness, truth, oneness, and beauty, are called transcendental, because they transcend, or exceed in extension, all the lower classes into which reality is divided.

(6) The Categories

Real Being is divided (not by strict logical division, but by a process analogous to it) into Finite and Infinite. Finite Being is divided into the supreme genera, Substance and Accident. Accident is further divided into Quantity, Quality, Relation, Action, "Passion", Place, Time, Posture, and Habit (or possession). These nine Accidents, together with the supreme genus, substance, are the ten Aristotelean Categories into which, as supreme classes, all Being is divided.

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